A white Light Emitting Diode (LED) is usually used as a backlight light source in a conventional liquid crystal display device, and generates a backlight for a liquid crystal display panel through a proper combination of a light guide plate and an optical film. With a growing demand for high color gamut, high color saturation and energy saving, the following solutions for achieving white light source, high color gamut and high color saturation in a backlight have been provided: combining an ultraviolet LED with red, green and blue phosphors; combining a blue LED with red and green phosphors; combining a blue LED, a green LED and a red LED; and the like. These solutions all can improve color gamut, but are difficult to be carried out and have a high cost.
A Quantum Dot (QD) technology is a semiconductor nanostructured material technology for bounding electrons in a certain range, and a QT is composed of ultra small compound crystals with a size of 1-100 nm. In the QT technology, crystals with different sizes can be used to control wavelength of light, thereby controlling color of light. Thus, when a QT material is applied to a backlight module, and a light source with high frequency spectrum (e.g., a blue LED) is used to substitute a typical white LED light source, the quantaum dot can be excited under a high frequency blue light source and generate light with different wavelengths. A color of the synthesized light can be adjusted by adjusting size of the quantum dot material, so that the backlight demand for high color gamut of the liquid crystal display device can be satisfied.
FIG. 1 illustrates a conventional backlight module using a quantum dot phosphor film. As shown in FIG. 1, a blue Light Emitting Diode (LED) 11 is disposed on a light incident side of a light guide plate 12, a quantum dot phosphor film 13 is disposed on a light extraction surface of the light guide plate 12, and light emitted from the blue LED 11 is converted into a surface light source through the light guide plate 12 and emitted from the light extraction surface thereof to pass through the quantum dot phosphor film 13, so that a blue light is converted into a backlight for the liquid crystal display device. However, in a liquid crystal display device having a large size, the quantum dot phosphor film 13 should be manufactured with a large area, and thus a lot of quantum dot material would be consumed, and a high coating uniformity of the quantum dot phosphor material is required, which causes a high cost. In addition, when the quantum dot phosphor film 13 is used, if the optical films have different frameworks or models, chrominance and luminance of light will vary greatly after the light improved by the optical films passes through a liquid crystal display plate, such that the framework, supplier or model of the optical film may not be easily changed during the use of the quantum dot phosphor film 13, which may greatly limit the use of the quantum dot phosphor optical film in flexibility and universality.
FIG. 2 illustrates another conventional backlight module using a quantum dot phosphor film. As shown in FIG. 2, a blue Light Emitting Diode (LED) 21 is disposed on a light incident side of a light guide plate 22, quantum dot phosphors are sealed in a glass tube to form a quantum dot phosphor glass tube 23, and the quantum dot phosphor glass tube 23 is disposed between the blue LED 21 and the light incident side of the light guide plate 22. Blue light emitted from the blue LED 21 is irradiated onto the light incident side of the light guide plate 22 through the quantum dot phosphor glass tube 23. However, in this way, the quantum dot phosphor glass tube 23 has a complex manufacturing process and a high cost, and the quantum dot phosphor glass tube 23 tends to broke.